1. Field of the Invention:
The present invention relates generally to mining apparatus, and, more particularly, to a rack assembly for advancing a winning machine used in underground mining.
2. Description of the Prior Art:
Conventional long wall mining procedures utilizing drum cutter mining machines to perform the winning operations require the assembly of a suitable surface to allow the mining machine to advance along the length of the mine wall. Rack assemblies have been developed and are well known in the art which operate to guide and to allow the advancement of the drum cutter mining machine along a mine wall.
A rack assembly is typically comprised of a plurality of discrete rack sections connected theretogether in order to allow the assembly to conform to the contour of the mine floor. One such example of a rack assembly is disclosed is West German Pat. No. DE-OS 2,224,478 which discloses a pin-toothed rack assembly. The discrete rack sections of the rack assembly disclosed therein are connected by means of ball joints connecting adjacent rack sections. Plates, links, or the like, are also utilized to interconnect sections of the support structure supporting the rack sections. These links or plates limit the relative vertical movement of the different sections of the support structure and the face conveyor. The links or plates further function to reduce the load exerted upon the ball joints which connect the adjacent rack sections, and, further, protect the ball joints from being damaged due to excessive force loads. The ball joints connecting the adjacent rack sections further function to insure that the pitch of the rack pins which meshingly engage with the drum cutter mining machine does not vary between adjacent rack sections.
Drum cutter mining machines are large, heavy machines, and movement of the mining machines along the rack assembly exerts large amounts of force upon the rack assembly. Additional force is exerted upon the rack assembly when the mining machine advances through hard seam zones. In such instances, the forces required to advance the machine often exceeds 550 kilonewtons (kN). Each individual rack section, and, additionally, each element connecting the discrete rack sections, must be capable of withstanding such forces. The ball joints such as those disclosed by West German Pat. No. DEOS 2,224,478 are incapable of repeatedly withstanding such force. To increase the size of such ball joints to ensure that no damage is sustained from forces of this magnitude, would require a ball joint of such a large size, that the use of such would be prohibited. An improved connecting means is therefore required in order to prevent damage to the rack assembly exerted during winning operations.
It is therefore the object of the present invention to provide a connecting means to connect discrete rack sections to form a rack assembly that is not susceptible to damage caused by the forces exerted during operation of a winning machine.
It is a further object of the present invention to provide a rack assembly which allows limited relative horizontal movement of discrete trough sections positioned beneath the rack sections.
It is a still further object of the present invention to provide a rack assembly which maintains individual pins on adjacent rack sections at a constant pitch even when high force loads of a winning machine are exerted thereupon.